The two battery packs for my Theragun Pro Gen 4 wouldn't charge so I opened the charging dock to take some measurements and found a burned resistor.
[image|3667422]
From the dimensions and code on the chip, it was a 100 ohm , 1/4 watt surtace mount device.
I replaced it with a 1/4 watt axial resistor and the dock was able to charge both my packs.[br]
(I had to solder tack wires to other points of the board since the surface mount pads were damaged by the overheating.[br]
I used a meter to trace where else I could attach the new resistor.
One end of the resistor went to a cap pad.
[image|3667424]
and the other end went to a diode pad)
[image|3667425]